Document Type : Original Paper
M.Sc. in Medical Physics, Tehran University of Medical Sciences, Tehran, Iran.
Associate Professor, Physics and Biomedical Engineering Dept., Research Center for Science & Technology in Medicine of Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran
Assistant Professor, Physics and Biomedical Engineering Dept., Research Center for Science & Technology in Medicine of Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran
Associate Professor, Radiology Dept., Faculty of Medicine, Johns Hopkins University, Baltimore, USA
Introduction: In this study, we utilized the MCNP4C Monte Carlo code to quantitatively evaluate the
influence of crystal size and material on intercrystal scatter and parallax effects.
Materials and Methods: For each of the 5 selected crystals (BGO, LSO, LYSO, LuAP, GSO), transport of
511 keV photons originating from a point source and incident on the central crystal of a block detector
consisting of a 13 × 13 array of 4 mm × 4 mm × 20 mm crystals was simulated. Functions such as position
detection accuracy (PDA) and point spread function (PSF) in different crystals were considered by changing
the parameters such as crystal thickness, crystal pixel size and gamma ray angle of incidence. The code was
validated against the simulated data published by Shao et al.
Results: The results of the simulations and their analysis showed that increasing the crystal pixel size
increased the PDA and decreased the ICS but increasing the crystal thickness decreased the PDA and
increased the ICS.
Discussion and Conclusion: By considering the attenuation properties of 511 keV photons, we conclude that
BGO is the most appropriate crystal for reducing the intercrystal scattering phenomenon. However, the
higher light yield and lower decay time of LSO and LYSO makes them the most appropriate crystals for use
in PET systems. The obtained functions for intercrystal scattering can be used for recovering spatial
resolution and improving image quality in the image reconstruction process.